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BULLOUGH, W. S. 1960. Practical invertebrate anatomy. 2nd ed. London: Macmillan.

FISCHER, P.-H. 1948. Données sur la résistance et de le vitalité des mollusques.—J. Conch., Paris 88: 100-140.

FISCHER, P.-H., DuvAL, M. & Rarry, A. 1933. Etudes sur les échanges respiratoires des littorines.—Archs

Zool. exp. gén. 74: 627-634.

Koun, A. J. 1960a. Ecological notes on Conus (Mollusca: Gastropoda) in the Trincomalee region of Ceylon.—

Ann. Mag. nat. Hist. (13) 2: 309-320.

Koun, A. J. 19605. Spawning behaviour, egg masses and larval development in Conus from the Indian

Ocean.— Bull. Bingham oceanogr. Coll. 17 (4): 1-51.

THIELE, J. 1910. Mollusca: B. Polyplacophora, Gastropoda marina, Bivalvia. In: SCHULTZE, L. Zoologische

und anthropologische Ergebnisse einer Forschungsreise im westlichen und zentralen Siid-Afrika 4: 269-270.

Jena: Fischer.— Denkschr. med.-naturw. Ges. Jena 16: 269-270.

(continued inside back cover)

ANNALS OF THE SOUTH AFRICAN MUSEUM

ANNALE VAN DIE SUID-AFRIKAANSE MUSEUM

Volume 69 Band

August 1975 Augustus

Part Zz Deel

THERMALLY ANOMALOUS

LATE PLEISTOCENE MOLLUSCS

FROM THE SOUTH-WESTERN CAPE PROVINCE,

SOUTH AFRICA

ANTHONY J. TANKARD

Cape Town Kaapstad

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ISBN 0 949940 70 4

Printed in South Africa by In Suid-Afrika gedruk deur

The Rustica Press, Pty., Ltd., Die Rustica-pers, Edms., Bpk.,

Court Road, Wynberg, Cape Courtweg, Wynberg, Kaap

THERMALLY ANOMALOUS LATE PLEISTOCENE MOLLUSCS FROM

THE SOUTH-WESTERN CAPE PROVINCE, SOUTH AFRICA

ANTHONY J. TANKARD

South African Museum, Cape Town

(With 3 figures and 2 tables)

[MS. accepted 29 May 1975]

ABSTRACT

Numerous exposures of Late Pleistocene marine sediments occur on the west and south

coasts of the Cape Province. The mollusc fauna, which includes some 124 species, only 3 of

which are extinct, lived in sediments deposited during the last interglacial. Two broad and

contemporaneous facies are recognized: a cool-water open-coast facies, and a warm-water

estuarine-lagoonal facies. Whereas the open-coast facies is characterized by molluscs which

presently live on the adjacent coast, the estuarine-lagoonal facies regularly contains tropical

species which lived far south of their known present-day geographic ranges. Differences in

distribution between the fossil warm-water molluscs and their present-day temperature-

sensitive counterparts have been used to interpret Late Pleistocene climatic change in the

south-western Cape. These deposits are correlated with the Mediterranean Eutyrrhenian.

CONTENTS

PAGE

Introduction : : : ‘ : : ; . 17

Geologic Setting . : : : : : : ; 18

Methods. : 5 ; : : : ; : 20

Palaeoecology. A : ; f , ; k P|

Population Dynamics : : : ; : ; 25

Predation ‘ : : ‘ ‘ : i‘ 29

Teratological Specimens ; : : ; 4 ; 31

Depthy’ =. : 3 : j , ‘ : d 31

Temperature. , : : : ; 3 : 32

Summary : ; : : : 37

Palaeoclimatic Interpretation : 4 ; : 38

Review of Present Climate and Hydrology ; i ; 38

Late Pleistocene Climate . : : : ; : 40

Discussion , : ; ; : ‘ ; , 41

Acknowledgements : ; J i ; ; ; 43

References . ; : : ; 4 ; ; : 43

INTRODUCTION

Isolated fossiliferous, marine sediments occur on the wave-cut platform

and in the sheltered Late Pleistocene embayments from Elands Bay on the west

coast to Knysna on the south coast. The fossils occur in unconsolidated

quartzose and shelly quartzose sands. The invertebrate fauna is essentially

modern in composition and comprises some 150 species which today live in

shallow-water environments. Only three of the mollusc species from the west

Ann. S. Afr. Mus. 69 (2), 1975: 17-45, 3 figs., 2 tables

18 ANNALS OF THE SOUTH AFRICAN MUSEUM

coast deposits are not known to be living today. In so far as most of these taxa

are still living, and are inhabitants of shallow water, they provide ideal material

for a palaeoecological study.

The Late Pleistocene fauna of the west coast is broadly divisible into two

distinct, but contemporaneous, ecologic zones. These are, firstly, a cool-water,

open-coast facies characterized by rocky shore and sandy beach assemblages,

and secondly, a warm-water, sheltered embayment facies (estuaries and lagoons).

Whereas the open-coast facies is laterally continuous, the sheltered embayment

facies is restricted in distribution. The open-coast facies is characterized by

molluscs which commonly inhabit the present coast. A striking feature of the

estuarine-lagoonal facies is the association of extant and extralimital thermo-

philic species. (“Thermophilic’ and ‘extralimital’ imply species which occur

outside their normal spawning range.) Examination of their present latitudinal

ranges indicates that a significantly warmer hydroclimate prevailed when those

species were common along the south-western Cape coast. In attempting to

reconstruct the palaeoenvironment, a detailed examination of a south coast

assemblage is necessary. The fossiliferous deposits at Knysna are therefore

included in the study.

Late Pleistocene faunas of open-coast and sheltered-embayment aspects

from southern California are similarly distinctive. Nearly all the dominant

species also inhabit the adjacent coast. But the sheltered embayments also

contain a high proportion of thermophilic molluscs which are found far north

of their present-day geographic range end-points. Several authors have used

these anomalies as a key to Late Pleistocene climatic interpretation (Valentine

1955, 1957, 1961; Valentine & Meade 1961; Addicott & Emerson 1959; Emerson

& Chase 1959; Kern 1971). Valentine (1955) explained the diverse nature of

the fauna by changes in intensity of the oceanic circulation and upwelling,

while the water of the embayments was heated by increased solar radiation. A

recent alternative explanation suggests that the larvae of tropical molluscs were

transported into the cooler areas by periodic local and temporary current

changes, and that they became only temporary, non-breeding, members of the

community (Zinsmeister 1974).

The south-western Cape Province, with its extensive Late Pleistocene

fossiliferous deposits, and its complex present-day ocean current systems, is

well placed to make a contribution to the knowledge of Late Pleistocene

hydroclimates. The purpose of this paper is to describe the mollusc fauna,

particularly between Ysterfontein and Elands Bay, and to examine their

palaeoenvironmental significance. The taxonomy of some of these molluscs

appears elsewhere (Kilburn & Tankard, in press).

GEOLOGIC SETTING

The Pleistocene epoch was characterized by the waxing and waning of

continental ice sheets with sea level oscillating in sympathy. Relative movement

of sea level is shown by the emerged wave-cut platforms, stranded beaches,

THERMALLY ANOMALOUS LATE PLEISTOCENE MOLLUSCS

Dar-es- Salaam

\ TANZANIA

St. Helena Bay

32°45 i)

Paternoster

Kruispad

Vredenburg

YASaldanha

aldanha

iers Bay

lopefield

Fig. 1. Locality map. The insert (partly after Boss 1969) shows the

distribution of present-day coastal forms: black =_ tropical;

stippled = warm-—temperate; area bounded by broken line on west

coast = cold water fauna.

20 ANNALS OF THE SOUTH AFRICAN MUSEUM

and marine terraces. Research on Barbados has suggested the existence of three

transgressions in the last interglacial (Eem): +6 m (BI) at 122 ka (i.e. 122 000

years ago); —13 m (BIJ) at 103 ka; —13 m (BIII) at 82 ka (Broecker et al. 1968).

These three peaks are confirmed by oxygen isotope studies of deep-sea cores

(Shackleton & Opdyke 1973).

Along the west coast of South Africa a thin mantle of Late Pleistocene

marine sediments overlies earlier Pleistocene, Tertiary, and pre-Tertiary rocks.

On the granitic headlands between St. Helena Bay and Ysterfontein a narrow

seaward-sloping wave-eroded platform is encountered. St. Helena Bay has

formed on Malmesbury rock which weathers more rapidly than the granite

and gives a negative relief. The open-coast fossil assemblages were collected

from marine deposits overlying the granite platforms, and from exposures in

the coastal flats bordering St. Helena Bay.

The last interglacial shorelines parallel the present coast very closely,

with two exceptions. Whereas the present coastline is interrupted only by

Saldanha Bay and its southerly offshoot, Langebaan Lagoon, the Late

Pleistocene sea extended up the Berg River valley and along Verlorevlei to

form two prominent estuaries. Verlorevlei is now separated from the sea by a

bar of Palaeozoic sandstone at 1 m a.s.]. (above mean sea level). These sheltered

Late Pleistocene estuaries and lagoons were of considerable palaeogeographic

importance since all fossil sites within them contain a significant proportion

of thermophilic molluse species.

The greatest observed thickness of the open-coast facies exceeds 5 m at

Velddrif; the greatest observed thickness of the estuarine facies is 2,2 m at

Verlorevlei. The open-coast facies consists of medium-grained quartzose sand

and comminuted shell. Frequently there are shell beds and banks with little

detrital quartz, indicating a slow supply of detrital sediment. A series of

emerged breaker-bars between Velddrif and Laaiplek parallel the modern

coast. These are composed largely of shell material.

In all the sheltered embayments the fossils are found in fine sands. At

Verlorevlei the marine horizon is overlain by coarse, poorly-sorted colluvium.

At Churchhaven the marine sediments are carbonate cemented and form an

erosional bench just above high-water level. Most of the sites examined, both

open-coast and sheltered embayment, are covered with a veneer of wind-blown

sand.

METHODS

The absolute density of fossil specimens of each molluscan species at any

particular site is difficult to determine because of the sampling problems

inherent on the size of the shell. For instance, ‘Rissoa’ capensis is a small

gastropod (usually less than 3 mm) and would frequently number in the

hundreds from just 100 g of sediment, while the large (approximately 200 mm)

Panopea glycymeris would occur at approximately 1 m intervals. Bearing in

mind that the present study is a palaeoecological one, and that the larger

THERMALLY ANOMALOUS LATE PLEISTOCENE MOLLUSCS Dh

molluscs have been better studied with respect to taxonomy and ecology,

emphasis has in all cases been placed on the macro-molluscs. A further

source of error arises from the differential fragmentation of shells. Bivalve

shells are more easily broken than gastropod shells, and in the living assem-

blage they may have been far more abundant than the faunal list suggests.

Table 1 should be taken only as an approximation to the original community

structure.

The procedures adopted in drafting Table 1 are as follows:

1. It was desirable to sample as small an area as possible to obtain not

only the absolute density of each species, but also to obtain restricted samples

for size-frequency analyses. In most cases a quadrat size of 1 square metre

has been found adequate, although quadrat size may have to be adjusted up or

down depending upon the relative abundance of specimens.

2. For a shell to be counted as an individual it must be nearly complete,

or so nearly so that the remainder could not be identified and counted separately.

Left and right valves of each bivalve species were counted separately, and the

highest count taken as the total number of individuals of that species in that

quadrat.

3. Each species has been recorded in Table | as percentage frequencies

in the sample where more than 50 individuals were counted. Where a total of

less than 50 individuals were counted they are recorded in Table | as ‘x’.

No attempt has been made to relate species to sediment texture since every

mollusc at some time must have been living among already dead and fragmented

shells. The substrate would thus consist of quartzose sand and _bioclastic

material ranging in size from complete shells to finely comminuted fragments.

PALAEOECOLOGY

In this paper past extensions of tropical and subtropical mollusc geographic

ranges are used as a basis for interpreting Late Pleistocene palaeotemperature

changes. These inferences are based only on fossils of still extant species, and

the assumption (Durham 1950) that stenothermal organisms are in general

more critically limited by minimum temperatures than by maximum tempera-

tures. The validity of such palaeotemperature inferences depends on the fossils

being preserved in the sediments in which they once lived.

In describing the relationship between the fossils, after death, and the

sedimentary environment, we define the following types of fossil assemblages:

1. Life assemblage: disturbance after death negligible (Hallam 1960).

2. Death assemblage:

(i) Indigenous: organic remains disturbed after death but not trans-

ported very far (Hallam 1960).

(ii) Transported: organic remains introduced from a neighbouring

contemporaneous or older environment.

3. Mixed assemblage: this comprises any combinations of the above

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possibilities, and is the general case (Hallam 1960). The status of this assemblage

is Clarified by describing it, for instance, as a mixed life and indigenous death

assemblage. In the present study this is the commonest case.

POPULATION DYNAMICS

Boucot (1953), Olson (1957), Craig & Hallam (1963), and Craig & Oertel

(1966) have attempted to discriminate between life and indigenous death

assemblages on the one hand and transported death assemblages on the other,

by using size-frequency distributions. According to Boucot an indigenous death

assemblage is characterized by a positively skewed distribution (large number

of small forms), while negative skewness or a normal distribution characterizes

the transported death assemblage. He suggested that negative skewness resulted

from winnowing of the smaller shells. Craig & Oertel (1966) question this and

maintain that the shape of the size-frequency distribution in a fossil population

depends principally upon the growth-rate and mortality-rate of the relevant

species. In this way negative skewness could arise from a decreasing growth-rate

with constant mortality-rate which would concentrate the older age-classes

in a few size-classes. Craig and Oertel suggest the following options:

Growth-rate Mortality-rate Size-frequency distribution

decreasing constant negative skewness

constant decreasing positive skewness

constant increasing flattening of curve, possibly

negative skewness

constant constant mirror image of living popul-

ation by dead population

Growth-rate and mortality-rate complement each other when one decreases and

the other increases, but cancel each other if both increase or decrease.

Higher mortality-rates which favour large populations may result from

a fluctuating environment (Valentine 1971). Mortality is affected by nutrients,

temperature, and salinity changes. In general, invertebrates have higher

mortality-rates in the early stages of life, but the rate may be lower in some

species than others (Craig & Oertel 1966). Environmental conditions in estuaries

and lagoons would be expected to fluctuate widely and rapidly. They would

be expected to show a variable salinity range due to evaporation and influx

of fresh water, and a high diurnal temperature range. Furthermore, seasonal

upwelling of cold water along the Cape west coast leads to marked instability

of the environment on the open coast too.

Although growth-rate is an important factor in this type of study, it is

one of the attributes about which there is little information. There is evidence,

however, that most bivalves maintain a slightly decreasing, but nearly linear,

growth-rate throughout life (Craig & Oertel 1966). This has been shown. to be

the case for Cardium edule, Tapes japonica, Dosinia exolata, and Venus striatula

(Kristensen 1959; Wilbur & Yonge 1964).

26 ANNALS OF THE SOUTH AFRICAN MUSEUM

The most likely effect of the unstable environmental characteristics of the

west and south coasts of the Cape would be a high mortality-rate among the

juvenile molluscs. Assuming a constant growth-rate for the bivalves, the inter-

play of mortality-rate and growth-rate should lead to a positively skewed

size-frequency distribution for a life assemblage, or an indigenous death

assemblage.

Besides the effect of growth-rate and mortality-rate on the shape of the

histogram, the assemblage may be affected by post-death mechanical change

such as sorting or winnowing by currents (Boucot 1953) and selective frag-

mentation, and solution of the smaller or thinner shells. Experience with the

west coast fossils shows that crushing and fracturing is of primary importance,

and affects the bivalves more than the gastropods.

The large number of fragmented shells in both the open-coast facies and

estuarine-lagoonal facies sediments suggests death assemblages that have

undergone considerable modification by wave-action. Whereas the open-coast

bivalves are usually disarticulated, those in the estuarine-lagoonal sediments

show a high degree of articulation. These sheltered embayment sites contain

epifaunal and infaunal molluscs, some of which are preserved in their living

positions. Size-frequency distributions for some of the bivalves are shown in

Figure 2. Since the warm-water element inhabited the Late Pleistocene lagoons

and estuaries, samples from those environments have been analysed in most

detail.

A single sample from a known high-energy open-coast site was examined in

detail. Figure 2A shows the size-frequency distribution for Venerupis senegalensis

from the Velddrif site. The field-setting suggests a transported death assemblage

in which vigorous wave-action piled shell debris up to form a breaker-bar.

In these deposits the thinner shells have generally been fragmented. The

V. senegalensis population is composed of thick-shelled forms. Its estuarine

ecomorph, on the other hand, has a thinner shell and is of more constant

morphology. The Velddrif V. senegalensis shows marked negative skewness

(—0,82). It has an articulation ratio less than 0,05. Articulation ratio is defined

as the ratio of complete shells/4 (RV+LYV).

Size-frequency distributions of bivalves from the estuarine-lagoonal facies

differ from the pattern of the Velddrif example. Tellina madagascariensis from

Verlorevlei (Fig. 2C) and Churchhaven (Fig. 2H) tends to have a flattened

histogram. The Verlorevlei Tellina has a size-peak at 64-66 mm, and the

Churchhaven specimens at 56-60 mm. While the narrower size range of the

Verlorevlei material (50-86 mm) suggests a transported death assemblage, the

greater range of the Churchhaven material (16-74 mm; more juveniles) suggests

an indigenous death assemblage. That this argument can be misleading is shown

by their articulation ratios of 1,46 and 0,47 respectively. At both of these

localities T. madagascariensis is associated with comminuted shells and dis-

articulated valves of other species. JT. madagascariensis at Verlorevlei was

observed in a nearly horizontal attitude as were the other bivalves. But whereas

THERMALLY ANOMALOUS LATE PLEISTOCENE MOLLUSCS

12 A 12

Dosinia lupinus RV

104 Venerupis senegalensis LV 104 Verloreviei (1) Art. rat. 040

Velddrif (9)

3 erat Art. rat. <Q05 8

N=50 No.

No® °

4 4

2 2

109 14518) 22) 82693034" 238) 42) P46) 50 Gin SI ONRI4 Sy enIS 22 eee 208 SO She 38)

Width (mm) Width (mm)

C 12

Tellina| madagascariensis 104 Dosinia lupinus

Verlorevlei (3) RV Verlorevlei (3)

Art. rat. 146 N=80

Art. rat. O1U

50 54 58 62 66 70 74 78 82 86 Gi lO REIG Sti 22226 ra SORSy 238)

eee, Sill

16 Gastrana matadoa

Verlorevlei (3) LV

N= 74 Art. rat. 256 F

Dosinia

lupinus

Kruispad (12)

N=7]

Art. rat. <Q05

by RV.

Bored valves

Art. rat. 0,47

RV Tellina| madagascariensis

Loripes liratula

Art. rat. (0.05 No.8} Churchhaven(21)

Kruispad (12)

N=71

4 4

2 2

{SOF Gk SB ME ay 162° (24) 9232, 7400482) S664: | 72

” I J

Dosinia lupinus Loripes liratula

204 Churchhaven (21) RV Knysna LV

Art. rat. 013 1a] N=89 Art. rat. €0,05

UNS ZZ, 5265 3035) 8 38 42

Fig. 2. Size-frequency distribution of selected bivalve shells.

28 ANNALS OF THE SOUTH AFRICAN MUSEUM

most bivalves burrow with the shell vertical, Tellina burrows rapidly and settles

in a horizontal position. For this reason the posterior end of the shell is strongly

flexed to the right so as to broaden the radius of curvature of the siphons to

minimize the current flow constriction. In a small quadrat at Verlorevlei

29 articulated shells were observed. Of these 26 had the right valve uppermost,

i.e. flexure upwards, and with the posterior end slightly raised. Many of the

T. madagascariensis shells still had the ligamental material attached across

both valves as a powdery residue. Clearly these animals must have died in their

life positions where the weight of sediment prevented opening of the shells

after relaxation of the adductor muscles. If they had opened after death and

subsequently closed again due to increased sediment load, the ligament would

have broken.

At Verlorevlei the T. madagascariensis (site 3) size-frequency distribution

can be compared with those of Gastrana matadoa and Dosinia lupinus (Fig. 2B,

D, E). Dosinia lupinus at site | (Fig. 2B) has a positively skewed (+0,37)

histogram with an articulation ratio of 0,40. The field occurrence suggests that

reworking of the sediment has taken place, although the shells are still situated

close to their original life habitat. Although the articulation ratio is high,

relative displacement of each valve is common. At site 3 the D. /upinus histogram

is bell-shaped (Fig. 2D). Here the articulation ratio is only 0,10. The bell-shaped

distribution suggests less winnowing of the small specimens. Both D. /upinus

populations peak at 22-24 mm. From site | to site 3 at Verlorevlei there is a

tendency for a greater spread of size-ranges of D. /upinus: 16-34 mm at site |

and 6-40 mm at site 3. Conceivably the histogram for D. /upinus (site 1) was

originally bell-shaped but winnowing may have removed the smaller sizes.

This is borne out to an extent by the increase in relative proportions of Loripes

liratula in the assemblage, from 9 per cent at site 1 to 26,4 per cent at site 3.

The size-range of L. /iratula 3-17 mm (Fig. 2G, J) coincides with the juvenile

fraction of D. lupinus. Because of the close similarity in shape of D. lupinus

and L. liratula, equal-size specimens of each species would be expected to be

hydraulically equivalent.

The size-frequency distribution of Dosinia lupinus at Churchhaven has a

tail towards the larger specimens (Fig. 21), suggesting winnowing. It has a

narrow size-range, 14-42 mm, and peaks at 28-30 mm. The low articulation

ratio (0,13) suggests reworking.

At Kruispad the Dosinia lupinus population again has a wide size-range,

6-40 mm (Fig. 2F), but an articulation ratio less than 0,05. Furthermore, the

histogram has two peaks, at 16-18 mm and 28-30 mm. The bimodal distribution

could be explained by extinction of one living population, followed by fresh

recruitment when environmental conditions improved. The site is 15 km up

the Berg River and could possibly have been influenced by sudden influxes of

fresh water. But Loripes liratula at this site appears to represent a single popula-

tion: the histogram is bell-shaped and peaks at 12-13 mm. Its low articulation

ratio (< 0,05) may be meaningless since this species does not have prominent

THERMALLY ANOMALOUS LATE PLEISTOCENE MOLLUSCS 29

dentition, and seldom in this study were articulated valves encountered. For

example, Loripes liratula from Knysna has an articulation ratio less than 0,05

although juveniles dominate. Craig (1967) found that of five species he examined,

only Divaricella quadrisulcata tended toward a normal distribution. (Divaricella

and Loripes are both Lucinidae.)

Gastrana matadoa (Fig. 2E) at Verlorevlei is positively skewed and has a

high articulation ratio (2,56). This high articulation ratio, compared with that of

Dosinia lupinus from the same site, could be due to the more robust dentition

of the former, but the greater proportion of juveniles of G. matadoa suggests

it probably is closer to a life assemblage.

In general, the sign of skewness alone as used by Boucot (1953) is insufficient

to distinguish between indigenous and transported death assemblages. The

field-setting shows the Velddrif breaker-bar deposit to contain a transported

death assemblage. It has strong negative skewness and a low articulation ratio.

This tail towards the left has been produced by winnowing of the finer fractions,

and effectively displacing the mode towards the coarser size-grades. The other

size-frequency distributions are suggestive of indigenous death assemblages

which have in most cases been slightly reworked. In Figure 2B the lack of

juveniles of Dosinia lupinus coincides with low numbers of the hydraulically

equivalent Loripes liratula.

Other indications that the shells are found in the sediment in which they

once lived include relatively high articulation ratios of the larger shells. Smaller

shells, e.g. Loripes liratula, tend to have weaker hinge attachments, while

juveniles of other species may have been subjected to predation. Tellina

madagascariensis at Verlorevlei appears to be in a life orientation, and also

has the ligamental material still attached. At Kruispad a bed contains Panopea

glycymeris still in the life orientation. The shells were all articulated, all posterior

end upwards, and all on the same horizontal plane, i.e. they had all burrowed

a siphon-length below the sediment-water interface. At most sites, left and right

valves were present in equal proportions.

In conclusion, the field-setting shows that open-coast assemblages are all

transported death assemblages, but transportation has been only local. The

faunas of the sheltered environments are mixed life and indigenous death

assemblages. Taken as a whole the fauna of the open-coast facies and the

estuarine-lagoonal facies are consistent with the inferred Late Pleistocene

environments.

PREDATION

Many of the bivalve shells are punctured by countersunk borings, 1-2 mm

in diameter, made by predatory gastropods. The bored bivalves include: Dosinia

lupinus, Tellina madagascariensis, Gastrana matadoa, Venerupis senegalensis,

Venerupis dura, and Ostrea algoensis. Crepidula capensis and Natica genuana

were the most frequently bored gastropods.

At Churchhaven 17 per cent of Dosinia lupinus and 17 per cent of Tellina

30 ANNALS OF THE SOUTH AFRICAN MUSEUM

madagascariensis were bored. In the case of the former an equal number of

right and left valves were bored, as would be expected in view of the fact that

it burrows in a vertical position. Analysis of predation on T. madagascariensis

reveals a very different pattern. Successfully bored valves fell into two size-

classes (Fig. 2H). The first group comprised juveniles with a size range

20-22 mm, and the second group adults with a size range 46-64 mm. Only

right valves of adults were bored, which is to be expected because this species

lives buried in sediment in a horizontal position and with right valve uppermost.

Craig (1967) found that the right valve of Tellina radiata was also preferentially

bored. The second group of 7. madagascariensis comprised juveniles in which

left valves were preferentially bored, although a few right valves were also

bored. The preferential boring of juvenile left valves could also be the result

of the burrowing characteristics. Te/lina is a rapid burrower (Stanley 1970).

Depth of burrowing would be controlled by length of the siphons, and for this

reason the juveniles would presumably live at shallower depths than the adults

and would possibly burrow more slowly. Subsequent current scour would

possibly reach only the juveniles and flip them over to leave them left valve

uppermost. This also suggests that, besides predation, the juvenile bivalves

would be more susceptible to environmental changes since they live closer

to the surface.

Most of the bored bivalve shells have only one hole, which is not surprising

since only one puncture is necessary to kill the animal. In a few cases two holes

per shell were encountered. As far as Tellina madagascariensis is concerned

the borings occur most frequently in the antero-dorsal half of the shell (Fig. 3).

It was also observed that all bored specimens of 7. madagascariensis at Church-

haven consisted of separate valves, while four bored articulated shells of Dosinia

lupinus were observed.

Of the gastropods, Crepidula capensis was the most extensively bored. Again

there was usually only one hole per shell, although up to three were recorded.

The reason why Crepidula capensis is so susceptible to predation is because

it lives exposed at the surface where it is an easy prey. Unlike the bivalves,

Crepidula does not appear to have any preferred area for boring (Fig. 3).

40mm

Fig. 3. Predation: distribution of borings on Tellina madagascariensis

(left), and Crepidula capensis (right).

THERMALLY ANOMALOUS LATE PLEISTOCENE MOLLUSCS 31

Crepidula capensis from the shell beds north of Laaiplek have smaller bored

holes (less than 1 mm) than other C. capensis or the bivalves.

It is difficult to isolate the species that would have been the predator,

although it seems probable that the borings were made by a gastropod. The

most likely predator would appear to be the buccinid Burnupena papyracea.

Where many bivalves were found to be bored at Churchhaven, B. papyracea was

very prominent. At Verlorevlei there was a total absence of B. papyracea and

no sign of predation on bivalves.

TERATOLOGICAL SPECIMENS

Teratological specimens are those that are outside the normal range of

variation of a species (Ager 1963). At most sites an occasional aberrant form

was observed, and it was found generally that Gastrana matadoa was the most

susceptible to damage during life. This was very apparent at Verlorevlei (site 3)

where 27 per cent of G. matadoa were in some way deformed, compared with

less than 2 per cent for Tellina madagascariensis. Perhaps this reflects the degree

of adaption of G matadoa to its niche, and that the environment at Verlorevle1

in particular did not favour this species.

DEPTH

Regional geomorphic analysis suggests that the depth of water reflected

in the strata of all open-coast and sheltered embayment sites examined could

not have exceeded 5 m. The Late Pleistocene estuarine-lagoonal facies is

dominated by intertidal deposits, and the open-coast facies by beach deposits.

At Velddrif there is a good exposure of a breaker-bar with a washover-fan

the top of which is probably a close approximation to high water spring tide.

At Churchhaven and Kraalbaai Callianassa burrows and crab-burrows are

still preserved, indicating an intertidal or shallow subtidal environment. The

ostracod fauna, too, is indicative of intertidal conditions.

Very few of the 124 species listed in Table 1 suggest water depths greater

than 25 m. Most of these species live today in intertidal and the uppermost

sublittoral zones. Less than 4 per cent of the fauna lives today in water deeper

than 25 m.

Of the open-coast assemblages Nassarius speciosus is today usually dredged,

although it is sometimes found intertidally. No more than a few isolated shells

were found. Erycina subradiata has been encountered at 26 m (Barnard 1964).

Other species have a wide depth range although they are common in the inter-

tidal zone. Nearly all species of Patella encountered at open-coast sites are

intertidal. Only P. miniata, P. tabularis, P. compressa are infratidal (Branch

1971). Other intertidal molluscs include: Littorina knysnaensis (above

HWN), Marginella capensis (low tide down), Bullia digitalis (follows the tide),

B. laevissima, Thais cingulata, Burnupena papyracea (below mid-tide), Perna perna

(mid-tide), Aulacomya ater (mid-tide to low tide on rocky shores), Choromytilus

meridionalis, Dosinia lupinus, Donax serra (burrows in surf beaches below

32 ANNALS OF THE SOUTH AFRICAN MUSEUM

mid-tide), Venus verrucosa (found on the surface at mid-tide). Depth ranges

are given by Day (1969).

Of the estuarine-lagoonal facies molluscs Ostrea algoensis prefers depths of

25-200 m, Tellina ponsonbyi prefers off-shore waters to depths of 95 m, and

Theora alfredensis has been dredged from depths below 70 m (Barnard 1964).

Ostrea algoensis and Theora alfredensis are common in this facies. Only one

Tellina ponsonbyi valve was found at Churchhaven, suggesting that this specimen

strayed into shallow water.

Most of the sheltered-embayment molluscs prefer very shallow or intertidal

water. These include the gastropods Patella spp., Littorina knysnaensis (HWN),

Turritella capensis (quiet water shallower than 3 m), Oxystele variegata,

Burnupena papyracea, Nassarius kraussianus (mud-banks and weed-beds of

estuaries); the bivalves Loripes liratula (muddy sand at low tide), Solen capensis

(muddy sand of estuaries), Venus verrucosa, Choromytilus meridionalis, Perna

perna, Aulacomya ater, Tellina madagascariensis (extensive infratidally), Dosinia

lupinus, Donax serra and Panopea glycymeris.

None of the constituents of the open-coast or estuarine-lagoonal facies

required water depths greater than about 25 m. Modern bathymetric ranges for

the species suggests maximum Late Pleistocene water depths at these sites of the

order of 0-5 m. This is consistent with the geomorphic evidence.

TEMPERATURE

Since the primary purpose of this paper is a discussion of a southerly

migration of tropical and subtropical mollusc species in the last interglacial,

the most important criteria are those indicative of temperature. Sea surface

temperature inferences may be made by comparing geographic ranges of living

molluscan species with those of their fossil counterparts. Although the fossil

fauna of the west coast is distinctly modern in character, the estuarine-lagoonal

facies assemblages regularly contain several species whose present-day dis-

tribution is restricted to tropical and subtropical waters. The modern geographic

range end-points of the thermophilic species that live further north on the west

African coast are separated by 2 000 km from the fossil occurrences in the

south-western Cape, so that the fossil assemblages contain species that do not

today live in association. Northward migration of the extralimital species was

probably induced by deteriorating environmental conditions. Since the geo-

graphic ranges of recent molluscs seem to be determined mainly by temperature

(Valentine 1955), it would appear that falling temperature was the compelling

factor. It could also be argued that lower temperatures accompanied the advance

of the Weischelian ice-sheets, in which case falling sea level would have drained

the Late Pleistocene estuaries and lagoons. But with reflooding of these

environments in Recent time, the thermophilic molluscs did not return.

Mollusc assemblages in the estuarine-lagoonal facies of the west and

south coasts contain a total of more than 20 species that do not sustain

populations in those areas today. West coast sites contain 15 such species,

THERMALLY ANOMALOUS LATE PLEISTOCENE MOLLUSCS

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THERMALLY ANOMALOUS LATE PLEISTOCENE MOLLUSCS 35

mainly bivalves. These extralimital molluscs, their present-day geographic

ranges, and minimum temperature tolerances are shown in Table 2.

It is often difficult to assess the minimum temperature tolerance of living

molluscs. Zinsmeister (1974) divides the normal biogeographic range of a

taxon into a spawning range, and a non-spawning range. The modern geographic

range of Ostrea atherstonei, from Saldanha to Bushmans River, implies’ a

minimum temperature tolerance of about 13°C. But it appears that present

temperatures in Saldanha Bay are too low for spawning (Korringa 1956).

Spawning experiments in this area have confirmed this, and suggest that the

oyster larvae may actually originate in an area of higher water temperature.

It is possible that several species of molluscs extend their geographic range

end-points by inhabiting local pockets of warm water such as estuaries. If this

is the case then the temperature minima shown in Table 2 may actually be too

low. It is not always clear from the literature whether the range end-points

are open-coast, estuaries or embayments. Other difficulties arise from taxonomic

problems. For instance, Macoma ordinaria and M. crawfordi may be geographic

variants of the Mediterranean M. cumana.

1. West coast estuarine-lagoonal facies

Because of physiographic changes at Verlorevlei and the lower reaches

of the Berg River, present temperature ranges would be meaningless standards

against which to measure Late Pleistocene changes. The present shoreline of

Langebaan Lagoon has changed little since the last interglacial, and present

temperatures at Churchhaven could be used as an approximation for the other

sites as well. Day (1959) gives a surface temperature range for Churchhaven

or ts;5-C to 37°C (HW) and 38;5°C (LW).

The fossil assemblage at Verlorevlei (site 3) is represented by 23 species

of molluscs, 6 of which are indicative of warm water. These 6 thermophilic

species constitute 42 per cent of the total individuals. The modern geographic

range of Loripes liratula (26,4 per cent of the fauna) is Mauritania to Angola

(Nicklés 1950), where its minimum temperature requirement would be 17-18°C.

Ostrea stentina (2,7 per cent), Tellina madagascariensis (8,1 per cent), Macoma

tricostata (< 1 per cent), and Venerupis dura (< 1 per cent) are also tropical

west African species and could not tolerate temperatures below about 17°C.

Gastrana matadoa (4,1 per cent) extends into water as cool as 14°C. Accepting

that stenothermal organisms are more critically limited by minimum tem-

peratures than by maximum temperatures (Durham 1950), it would appear

that the minimum temperature in this Late Pleistocene estuary must have been

17-18°C, or at least 3°C warmer than present Churchhaven surface temperatures.

At Kruispad (site 12) 8 of the 31 species prefer warm water, and constitute

47,9 per cent of the total individuals. Of these Nuculana bicuspidata (3,2 per cent),

Loripes liratula (15,4 per cent), and Leporimetis hanleyi (1,0 per cent) have a

minimum temperature requirement of 17-18°C. A significant constituent of

this assemblage is Panopea glycymeris. Although it forms less than 1 per cent

36 ANNALS OF THE SOUTH AFRICAN MUSEUM

of the total individuals, it is nevertheless very common (because it is a large

animal, about 200 mm, and is always found in life orientation, a shell count in

a 1 m quadrat would be unlikely to yield more than one or two specimens).

Panopea glycymeris lives in areas with a temperature range 20-27°C (Kensley

1974), although it could probably tolerate cooler water. This assemblage is thus

indicative of a temperature minimum of about 18°C. At Bloemendal (site 11)

Loripes liratula and Leporimetis hanleyi are common.

Three sites examined along the shore of Langebaan Lagoon yielded a

significant proportion of thermophilic molluscs: Geelbek (site 19; 7 species in

26 constituting 46,0 per cent of the fauna), Skrywershoek (site 20; 6 species in

19 constituting 32,9 per cent of the fauna), and Churchhaven (site 21/22;

7 species in 31 constituting 28,1 per cent of the fauna in the lower unit; 7 species

in 27 constituting 35,5 per cent of the fauna in the upper unit). The dominant

thermophilic mollusc content at these sites is as follows:

Geelbek Skrywershoek — Churchhaven

Lower Upper

7 7o 7 7o

Ostrea atherstonei ay et 1,0 5,0

Loripes liratula 20,4 14,1 1,0 4,1

Mactra ovalina 1,0 182 23 Lod

Tellina madagascariensis 10,2 9,4 23,4 853)

Leporimetis hanleyi — <wkO — =

Venerupis dura 4,1 1,2 a —

All of these species, except Ostrea atherstonei and Mactra ovalina, have a

minimum temperature requirement of 17°C. Ostrea atherstonei is found living

today in Saldanha Bay, but temperatures are apparently too low for spawning.

It is possible that this species has a minimum temperature tolerance of 14°C.

The floor of the present lagoon is underlain by about 3 million metric tons of O.

atherstonei shells, with little detrital sediment, suggesting optimum temperatures

for breeding, and hence probably greatly in excess of 14°C. Mactra ovalina

has a minimum requirement of 19°C. A minimum temperature in the Late

Pleistocene lagoon of about 18°C is indicated, about 4-5°C warmer than the

present surface temperature minimum at Churchhaven.

2. South coast estuarine—lagoonal facies

A Late Pleistocene site at Knysna was the only one on the south coast

examined in detail. But examination of material in collections of the South

African Museum shows that very similar fossil faunas exist at Sedgefield, and

Groot Brak and Klein Brak estuaries. The fossil assemblage at the Klein Brak

estuary contains Panopea glycymeris, but their shells are, on average, much

smaller than the Kruispad specimens (Kensley 1974).

THERMALLY ANOMALOUS LATE PLEISTOCENE MOLLUSCS 37]

The Knysna assemblage contains 47 molluscan species, of which 6 are

extralimital and which constitute 60,4 per cent of the individuals. But these 6

species include the extinct subspecies Cantharidus suarezensis fultoni (9,8 per

cent) and Cerithium scabridum rufonodulosum (16,3 per cent). Although the

geographic ranges of the species is shown in Table 2, it is obviously not certain

that the extinct subspecies had the same temperature tolerances. Their Recent

relatives Cantharidus suarezensis suarezensis and Cerithium scabridum have

minimum temperature requirements of 19°C and 24°C respectively. Atys

cylindrica (<1 per cent) has a minimum temperature requirement of 21°C.

Of the bivalves Felania diaphana (3 per cent), Tellina madagascariensis (< 1 per

cent), Leporimetis hanleyi (< 1 per cent) and Venerupis dura (< 1 per cent) all

suggest temperature minima of 17°C. Loripes liratula (57,5 per cent) also

suggests a temperature minimum of 17°C, but the fact that it occurs in such

great numbers, and the fact that all growth stages are present (Fig. 2J), suggest

optimum conditions. Together the evidence suggests a temperature minimum

in excess of 17°C for the Late Pleistocene estuary. Day et al. (1952) gives a

temperature range at the railway bridge of 12—24°C.

3. West coast open-coast facies

The present-day temperature range on the adjacent open coast is about

13-15°C (Shannon 1966). The fossil assemblage contains only three species

which prefer warm water, but which never constitute more than | per cent of

any assemblage: Cypraea algoensis, Marginella piperata and Scissodesma

spengleri. The marked paucity of warm-water species indicates that Late

Pleistocene nearshore water temperatures were not very different from the

present.

SUMMARY

Before discussing the palaeoclimatic significance of the extralimital

molluscan species it may be as well briefly to summarize the evidence.

1. All fossiliferous Late Pleistocene estuarine-lagoonal facies deposits

contain extralimital species which usually constitute more than 30 per cent

of the individuals of each assemblage, and which indicate minimum water

temperatures 4-6°C warmer than the present-day estuaries and lagoons, with

minimum temperatures of about 18°C. Kanakoff & Emerson (1959) suggest

temperatures in excess of 19°C for similar Californian occurrences.

2. All growth stages of the thermophilic molluscs are present (Fig. 2).

The importance of this is that it implies that temperatures were such that the

normal spawning range of each mollusc is represented. Normal spawning range

is characterized by a population which continually maintains its numbers

(Zinsmeister 1974). The large number of individuals and presence of all growth

stages show that the thermophilic taxa formed self-sustaining populations that

were adequately adapted to the depositional environment.

3. The estuarine-lagoonal facies contain mixed life and indigenous death

38 ANNALS OF THE SOUTH AFRICAN MUSEUM

assemblages of molluscs. These molluscs obviously lived in environments

reflected in the sediments, and have suffered little post-death transportation.

4. The sediments and their mollusc fossils indicate water depths in general

less than 5 m.

5. The fact that sediments with high proportions of extralimital molluscan

species characterize most Late Pleistocene estuary and lagoonal situations,

that these molluscs formed self-sustaining populations and inhabited very

shallow water, suggests that the marine transgression to 6 m in the last inter-

glacial was a major event during a climatic optimum.

Zinsmeister (1974) has suggested that similar, well documented occurrences

of thermophilic molluscs in Californian Late Pleistocene embayments represent

only temporary, non-breeding, members of the community. He believes that

periodic local and temporary current changes introduced tropical mollusc larvae

into areas of cooler water, and that these molluscs represent only temporary

members of the community since temperatures would have been too low for

them to maintain self-sustaining populations.

Zinsmeister’s arguments stem from the fact that previous studies paid

scant attention to the population dynamics, and consequently they fail to

prove the presence of self-sustaining populations. Similar occurrences in the

south-western Cape support the view that these faunas are the result of a warmer

climate which must have affected the whole world. Age-wise these deposits

are also similar and probably coincide with a high climatic peak (substage 5e)

and sea level up to 7 m higher than present at 120 ka (Shackleton 1969).

6. Configuration of the coastline was probably very important. Today

a low Palaeozoic rock bar just above high-tide level keeps the sea out of

Verlorevlei. A slight rise of sea level would create radical changes at Verlorevlei.

Likewise the lower reaches of the Berg River formed a prominent estuary due

to flooding by last interglacial high sea levels. Normally one would expect to

find an overlap of geographic ranges of tropical and temperate species. In

an overlap area the tropical species would be restricted to inshore, protected

environments, and temperate species would live in the cooler open coast sites

(Emerson 1956).

PALAEOCLIMATIC INTERPRETATION

REVIEW OF PRESENT CLIMATE AND HYDROLOGY

The south-western Cape has a Mediterranean-type climate. Hot, dry

summers are the result of the dominant anticyclones in those months, while

depressions associated with westerly winds bring rainfall in winter.

Hart & Currie (1960) have summarized the effect of the wind system on

the climate of the south-western Cape Province. A subtropical high-pressure

system is centred between 26° and 30°S. To the south this high-pressure system

borders on the ‘westerlies’ causing a steep pressure gradient. The south-easterly

winds of the south-western Cape are the result of winds blowing anticyclonically

THERMALLY ANOMALOUS LATE PLEISTOCENE MOLLUSCS 39

around this high-pressure system. In summer the centre of the anticyclone lies

at about 30°S and brings strong south-easterly winds to the south-western

regions, but in winter it moves northwards to 26°S. The westerly wind system

follows the anticyclone northward and the southern Cape is then frequented

by depressions which bring rain from the south-west Atlantic, although the

Namib Desert is still influenced by the Trade Wind belt.

The west coast of southern Africa, like the west coasts of other countries

in similar latitudes, is characterized by a linear belt of centres of upwelling of

cold subsurface water (Central Water) from Liideritz to the Cape Peninsula

(Fig. 1 insert). There is a north-south isotherm lineation with the coldest and

least saline water near the coast (Shannon 1966). This upwelling, the Benguela

Current, varies in intensity depending upon the wind system and local

topography. The upwelling phenomenon arises from the displacement of

surface water northwards and off-shore by the south-easterly wind system.

Cooler subsurface water wells up to replace this warmer water. The result

of this active upwelling is a complex system with tongues of cold water

alternating with intrusions of warmer oceanic waters, and all diverging to the

north-west (Bang 1971). Bang defines the Benguela Current as the area east of a

belt of off-shore divergence within which the oceanic processes are dominated

by short-term atmospheric interactions.

During the winter months when the anticyclone centre moves northward,

weakening of the southerly wind component results in weakening of the

upwelling system also. With less upwelling the surface waters over the inner

part of the continental shelf are warmer by 2°C, but off-shore a drop in

temperature tends to minimize this affect. With weakening of the Benguela

Current system and the greater prominence of westerly and north-westerly

winds, a southward-flowing inshore counter-current develops. Shannon (1966)

mentions a predominantly southward-flowing counter-current between

Lambert’s Bay and Cape Point which is present during all seasons, but most

marked in winter. A southward-flowing counter-current carries ‘seeboontjies’

from Angola and driftwood from the Orange River southwards (Wagner &

Merensky 1928). Surface temperatures at the Orange mouth rise noticeably

when the north-westerly winds blow.

The highest surface-water temperatures are encountered in the lagoons

and estuaries which are protected from the effects of upwelling. The temperature

range in Langebaan Lagoon, 10-39°C (Day 1959), contrasts markedly with

that of the near-by open sea, 13-15°C (Shannon 1966). During the summer

months temperatures in Langebaan Lagoon are at a maximum, while those

of the open sea drop.

The currents off the east and south coasts, the Mozambique Current and

Agulhas Current, have been studied by Clowes (1950), Orren (1963, 1966),

and Darbyshire (1964). Both of these currents are southward extensions of the

great South Equatorial Current which flows westwards across the Indian Ocean.

At 26°S the Mozambique Current is met by the southern branch of the South

40 ANNALS OF THE SOUTH AFRICAN MUSEUM

Equatorial Current, which is divided by Madagascar, and they combine to

form the Agulhas Current. The Agulhas Current is finally deflected by the

Agulhas Bank (Clowes 1950) (Fig. 1).

Upwelling does take place off Cape Agulhas but it is a geostrophic

upwelling, i.e. the upwelling varies with the velocity of the current. Here the

Agulhas Current is weakest and Agulhas water retreats northwards in winter,

thus allowing Central Water to reach the surface. In summer, when the Agulhas

Current is flowing at its strongest, it overrides the Central Water (Darbyshire

1964). Sometimes in summer the warm Agulhas Current moves away from the

south coast and allows cold Central Water to replace it inshore, and within

a day or two the temperature may fall by as much as 10°C (Day 1963). Schell

(1968) describes the occasional penetration of the Agulhas Current round the

Cape Peninsula into the South Atlantic.

LATE PLEISTOCENE CLIMATE

It would be expected that the intensity, and probably position, of the

anticyclones would vary with the solar radiation. A climatic optimum at 120 ka

produced temperatures warmer than at any other time in the last 120 ka

(Shackleton 1969). The anticyclone would have moved south of latitude 30°S

(Van Zinderen Bakker 1967: fig. 6). This would lead to the linear west coast

upwelling belt moving south in response, and the winter-rainfall area would

be more strictly restricted to the south-western Cape. Such a southward move-

ment would be accompanied by more pronounced upwelling off the west

coast than at present, and would operate over a longer period of time just

as happens on the Namib Desert coast. Since the Central Water originated

in the Southern Ocean, and since the Antarctic ice-sheet was essentially stable

throughout the Pleistocene (Mercer 1968), it is unlikely that the upwelling water

would have been any colder than the present. This is confirmed by the fossil

molluscs from the open-coast facies which suggest little temperature change.

Addicott & Emerson (1959) and Valentine (1955) have also suggested intensified

nearshore upwelling and a poleward expansion of isotherms to explain their

mollusc faunas.

Eustatic rise of sea level would have changed the configuration of the

coast by forming salt-water estuaries at Verlorevlei and the Berg River, as

well as at numerous sites along the south coast. The present coast is not as

embayed as the Late Pleistocene coast would have been. Thermally anomalous

assemblages existed contemporaneously only in the vicinity of the protected

bays where the increased solar radiation of the last interglacial heated the

surface water considerably.

Periodic current changes permitted the introduction of tropical mollusc

larvae into these pockets of warm water. The intensification of atmospheric

circulation that led to more pronounced upwelling presumably also affected

the inshore counter-current which possibly flowed more strongly than at present.

Isaacs & Sette (1959) described anomalous wind fields in the Pacific area during

THERMALLY ANOMALOUS LATE PLEISTOCENE MOLLUSCS 4]

1957 and 1958 which so changed the oceanic circulation that tropical taxa

were found far north of their expected ranges. This demonstrates that circulation

changes as proposed in this paper do happen at present, albeit less frequently

and less pronounced than is here suggested.

On the east coast with intensification of the air circulation intensification

of the present summer conditions would also be anticipated. Presumably the

Agulhas Current flowed more strongly than today and continually overrode

the Central Water, perhaps with frequent eddies of Agulhas water around the

Cape Peninsula. This would limit the likelihood of sudden incursions of cold

water, such as presently affect the Knysna estuary in summer and cause

temperatures to drop between 10 and 15°C (Korringa 1956).

These possible changes in the oceanic circulation during the hyperthermal

period would have had far-reaching effects on the distribution of molluscs.

Because of the low migratory ability of molluscs in the post-larval stage, their

geographic distribution depends primarily on the dispersion of larvae. Distribu-

tion of the planktonic larvae depends upon ocean currents. About 85 per cent

of tropical marine molluscs have a free-swimming pelagic larval stage which

can exist, on average, three to four weeks before settling (Zinsmeister 1974).

Dietrich (1935 in Korringa 1956) gives the velocity of the Agulhas Current as

50 km per day. At this rate larvae could be transported 1 000 km before

metamorphosis. Larvae can apparently withstand sudden changes of

temperature; Korringa mentions a change from 25° to 2°C which did not

adversely affect oyster larvae.

A general southward movement of isotherms on the west and south coast is

envisaged. This would have brought the tropical mollusc zone closer to the south-

western Cape. Periodic expansions of the warm-water isotherms coupled with an

intensified inshore counter-current on the west coast would have enabled

tropical mollusc larvae to pass the cold Benguela barrier. If the larvae reached

the sheltered estuaries and lagoons of the south-west coast, increased solar

heating (substage 5e) would have allowed these molluscs to sustain their

populations and persist there even after the open-coast thermal barrier became

impassable again. Those thermophilic larvae that reached metamorphosis

on the open coast may well have survived, but there is no evidence that they

were able to sustain their populations. South coast estuarine facies show that

larvae from the tropical west African coast were able to pass the Cape Pen-

insula: e.g. Tellina madagascariensis, Loripes liratula, Leporimetis hanleyi,

Venerupis dura, Panopea glycymeris. The Agulhas Current was also able to

transport Indo-Pacific mollusc larvae around the Peninsula to the west coast

sites. In these sheltered embayments warm-water taxa survived as relicts.

DISCUSSION

The occurrence of thermophilic molluscs in Late Pleistocene sediments

of the south-western Cape far beyond their present-day geographic range

end-points is not unique. Similar occurrences in California have been extensively

42 ANNALS OF THE SOUTH AFRICAN MUSEUM

studied, and the same conditions appear to have operated in the Miocene

where the configuration of the coastline was very different from the present.

The San Joaquin basin was a protected embayment in the Late Miocene, and

there relict faunas persisted long after the temperate faunas had spread south-

ward along the open coast (Addicott & Vedder 1963). The thermally anomalous

Late Pleistocene molluscs also lived in shallow protected embayments (Addicott

& Emerson 1959). The only significant point of difference between the two

regions is that the open-coast facies of the Cape coast contains molluscs which

nearly all live on the adjacent coast, while the Californian open-coast facies

contains a fauna that reflects cooler water than the present. Valentine (1955)

proposed that during the last interglacial of California upwelling was intensified,

while at the same time the warmer water of the sheltered embayments was

derived from increased solar radiation. He also suggested a general warming

of the oceanic waters by increased solar heating.

‘ The Late Pleistocene estuarine-lagoonal facies of the Cape Province are

attributed to a eustatic rise of sea level which changed the configuration of the

coast and produced a great number of estuaries where the effects of seasonal

upwelling were excluded. A southward movement of the south Atlantic anti-

cyclone at this time shortened the cold-water barrier on the western open

coast by causing a southward shift of the Benguela Current, and possibly

strengthened the inshore counter-current, so that thermophilic mollusc larvae

were able to migrate southwards where they could sustain their populations

in the solar-heated estuaries and lagoons. It would appear that the present

temperatures are too low for breeding.

This history contrasts with that of the Early Pleistocene when sea

temperatures on the open coast were much warmer than at present. The last

of these warm-water open-coast episodes is associated with the 45-50 m trans-

gression complex of the Namaqualand coast (Carrington & Kensley 1969).

Striostrea margaritacea was common on the open coast, forming the so-called

‘oyster line’ (Haughton 1931). This oyster requires a minimum water temperature

of 25°C in summer (Korringa 1956). The 45-50 m transgression complex

sediments were probably pre-glacial Pleistocene. Such warm conditions must

have been in response to the warmer conditions prevailing in the northern

hemisphere, since the Antarctic ice-sheet is thought to have been stable through-

out the Pleistocene (Mercer 1968). Warming of the northern hemisphere would

have moved the intertropical convergence farther south than even its Late

Pleistocene position. This would have moved the South Atlantic anticyclone

south, and with it the belt of upwelling, bringing tropical waters down the

Namaqualand coast. But Striostrea margaritacea is totally absent from Early

Pleistocene deposits in the Saldanha area, suggesting that cool water, and

upwelling, were still dominant there.

If the model for a southward shift of the anticyclonic system in the last

interglacial is correct, then one would expect the opposite trend during the

Weischelian. Lamb (1961) suggests that Ice Age circulation was marked by

THERMALLY ANOMALOUS LATE PLEISTOCENE MOLLUSCS 43

intensified circulation of the belt of westerlies, and greater mobility in the

subtropical anticyclones, which generates upwelling systems such as the Benguela

Current. Van Zinderen Bakker (1967, in press) presents evidence to show that

during hypothermal periods the influence of the anticyclones and the Benguela

Current would have shifted northwards to the equatorial regions. Displacement

of the westerlies towards lower latitudes would have expanded the winter-

rainfall area of the southern Cape, and would have caused a northerly shift

of the Namib Desert. Tankard & Schweitzer (1974) have demonstrated, from

Die Kelders cave sediments, that wetter conditions in the Weischelian coincided

with a cooler period. Butzer (1973) has found a similar record in the Nelson

Bay cave. A northward migration of the belt of westerlies would have resulted

in a longer rainy season, if not year-round precipitation.

Finally, this study suggests a possible correlation of the last interglacial

deposits of the Cape Province with the Eutyrrhenian of the Mediterranean.

Although warping of the Eutyrrhenian shorelines is universal (Richards 1962),

Bonifay & Mars (1959) have attempted to restore these shorelines to their

original elevations. They attribute the Eutyrrhenian shoreline to a transgression

to 2-3 m a.s.]. Chronologically the Eutyrrhenian shoreline and last interglacial

shorelines of the south-western Cape appear to be similar.

The Strombus fauna of the Eutyrrhenian deposits is characterized by

Strombus bubonius and other species typical of Senegal and west Africa

(Richards 1962) which suggest warmer hydroclimates than today. Like the

warm water fauna of the south-western Cape, the Strombus fauna can also be

attributed to poleward expansion of isotherms, and once in the Mediterranean

the molluscs remained a relict fauna which survived in water heated by increased

solar radiation.

ACKNOWLEDGEMENTS

The writer wishes to thank Mr R. N. Kilburn for his assistance in

identifying some of the molluscs and Mr V. Branco who assisted with the

illustrations. This research project was supported by a grant from the

CS:ER.

REFERENCES

AppicoTt, W. O. & Emerson, W. K. 1959. Late Pleistocene invertebrates from Punta Cabras,

Baja California, Mexico.—Am. Mus. Novit. 1925: 1-33

Appicott, W. O. & VEDDER, J. G. 1963. Paleotemperature inferences from late Miocene

mollusks in the San Luis Obispo—Bakersfield area, California. — Prof. Pap. U.S. geol. Surv.

475C: 63-68.

Acer, D. V. 1963. Principles of Paleoecology. New York: McGraw-Hill.

BANG, N. D. 1971. The southern Benguela Current region in February, 1966: Part Ii. Bathy-

thermography and air-sea interactions.— Deep-sea Res. 18: 209-224.

BARNARD, K. H. 1964. Contributions to the knowledge of South African marine Mollusca.

Part V. Lamellibranchiata.— Ann. S. Afr. Mus. 47: 361-593.

Boniray, E. & Mars, P. 1959. Le Tyrrhénien dans le cadre de la chronologie quaternaire

méditerranéenne. — Bull. Soc. géol. Fr. (7) 1: 62-78.

44 ANNALS OF THE SOUTH AFRICAN MUSEUM

Boss, K. J. 1969. The subfamily Tellininae in South African Waters (Bivalvia, Mollusca). — Bull.

Mus. Comp. Zool. 138: 81-162.

Boucor, A. J. 1953. Life and death assemblages among fossils.— Am. J. Sci. 251: 25-40.

BRANCH, G. M. 1971. The ecology of Patella Linnaeus from the Cape Peninsula, South Africa.

1. Zonation, movements and feeding.— Zoologica Afr. 6: 1-38.

BROECKER, W. S., THURBER, D. L., GODDARD, J., KU, T-L., MATTHEWS, R. K. & MESOLELLA,

K. J. 1968. Milankovitch hypothesis supported by precise dating of coral reefs and deep-

sea sediments. — Science 159: 297-300.

ButTzer, K. W. 1973. Geology of Nelson Bay Cave, Robberg, South Africa.—S. Afr. archaeol.

Bull. 28: 97-110.

CARRINGTON, A. J. & KENSLEY, B. F. 1969. Pleistocene molluscs from the Namaqualand

coast.— Ann. S. Afr. Mus. 52: 189-223.

Cowes, A. J. 1950. An introduction to the hydrology of South African waters.—JInvestl.

Rep. Fish. Mar. biol. Surv. Div. Un. S. Afr. (12): 1-42.

Craic, G. Y. 1967. Size-frequency distributions of living and dead populations of pelecypods

from Bimini, Bahamas, B.W.I.—J. Geol. 75: 34-45.

Craic, G. Y. & HALLAM, A. 1963. Size-frequency and growth-ring analyses of Mytilus edulis

and Cardium edule, and their palaeoecological significance.— Palaeontology 6: 731-750.

Craic, G. Y. & OERTEL, G. 1966. Deterministic models of living and fossil populations of

animals.— Q. J. geol. Soc. Lond., 122: 315-355.

DarsysHIRE, J. 1964. A hydrological investigation of the Agulhas Current area.— Deep-sea

Res. 11: 781-815.

Day, J. H. 1959. The biology of Langebaan Lagoon: a study of the effect of shelter from wave

action. —Trans. r. Soc. S. Afr. 35: 475-547.

Day, J. H. 1963. The complexity of the biotic environment.—Publs. Syst. Ass. (5): 31-49.

Day, J. H. 1969. A guide to the marine life of South African shores. Cape Town: A. A.

Balkema.

Day, J. H., MILLARD, N. A. H., & HARRISON, A. D. 1952. The ecology of South African

estuaries. Part III, Knysna: a clear open estuary.—Trans. r. Soc. S. Afr. 33: 367-413.

DuruaM, J. W. 1950. Cenozoic marine climates of the Pacific coast.— Bull. geol. Soc. Am. 61:

1243-1264.

EMERSON, W. K. 1956. Pleistocene invertebrates from Punta China, Baja California, Mexico.

— Bull. Am, Nat. Hist. 111: 313-342.

EMERSON, W. K. & CHASE, E. P. 1959. Pleistocene mollusks from Tecolote Creek, San Diego,

California.— Mem. S. Diego. Soc. nat. Hist. 12: 335-346.

GRANT, U.S. IV & GALE, H.R. 1931. Catalogue of the marine Pliocene and Pleistocene Mollusca

of California and adjacent regions.— Mem. S. Diego Soc. nat. Hist. 1: 1-1036.

HALLAM, A. 1960. A sedimentary and faunal study of the Blue Lias of Dorset and Glamorgan.

—Phil. Trans. r. Soc. Lond. B 243: 1-44.

Hart, T. J. & Currie, R. I. 1960. The Benguela Current.— Discovery Rep. 31: 127-297.

HAUGHTON, S. H. 1931. The late Tertiary and Recent deposits of the west coast of South

Africa. — Trans. geol. Soc. S. Afr. 34: 19-57.

Isaacs, J. D. & SetTTE, O. E. 1959. Unusual conditions in the Pacific. — Science 129: 787-788.

KANAKOFrF, G. P. & EMERSON, W. K. 1959. Late Pleistocene invertebrates of the Newport

Bay area, California.—Contr. Sci. 31: 1-47.

KENSLEY, B. F. 1973. Sea-shells of southern Africa—gastropods. Cape Town. Maskew Miller.

KENSLEY, B. F. 1974. The status of the Plio-Pleistocene Panopea in Southern Africa (Mollusca,

Bivalvia, Hiatellidae).— Ann. S. Afr. Mus. 65: 199-215.

KERN, J. P. 1971. Paleoenvironmental analysis of a Late Pleistocene estuary in southern

California.—J. Paleont. 45: 810-823.

KILBURN, R. N. 1971a. On some species of the families Tonnidae, Hipponicidae, Buccinidae,

Columbariidae, Fasciolariidae, Psammobiidae and Mactridae (Mollusca) in South African

waters. Ann. Natal Mus. 20: 483-497.

KILBuRN, R. N. 19715. A revision of the littoral Conidae (Mollusca: Gastropoda) of the

Cape Province.— Ann. Natal Mus. 21: 37-54.

KILBURN, R. N. & TANKARD, A. J. 1975. Pleistocene molluscs from the west and south coasts

of the Cape Province, South Africa. Ann. S. Afr. Mus. 67: 183-226.

KorrInGA, P. 1956. Oyster culture in South Africa.—Jnvestl. Rep. Div. Sea Fish., S. Afr.

20: 1-86.

THERMALLY ANOMALOUS LATE PLEISTOCENE MOLLUSCS 45

KRISTENSEN, J. 1959. The coastal waters of the Netherlands as an environment of Mollusca

life. —Basteria 23 (Suppl.): 18-55.

Lams, H. H. 1961. Fundamentals of climate. In: Nairn, A.E.M. ed. Descriptive palaeo-

climatology: 8-44. New York: Interscience Publishers.

Mercer, J. H. 1968. Antarctic ice and Sangamon sea level.—Pub/. int. Ass. scient. Hydrol

79: 217-225.

Nick.es, M. 1950. Mollusques testacés marins de la céte occidentale d’ Afrique. Paris: Lechevalier

OLSON, E. C. 1957. Size-frequency distributions in samples of extinct organisms.—J. Geol. 65:

309-333.

OrrEN, M. J. 1963. Hydrological observations in the South West Indian Ocean. —Jnvestl. Rep.

Div. Sea Fish., S. Afr. 45: 1-61.

OrrEN, M. J. 1966. Hydrology of the South West Indian Ocean. —Jnvest/. Rep. Div. Sea Fish.,

S. Afr. 55: 1-35. 5

RIcHARDS, H. G. 1962. Studies on the marine Pleistocene:

Part 1. The marine Pleistocene of the Americas and Europe.

Part 2. The marine Pleistocene mollusks of eastern North America. —

Trans. Am. phil. Soc. 52 (3): 1-141.

ScHELL, I. I. 1968. On the relation between the winds off Southwest Africa and the Benguela

Current and Agulhas Current penetration in the South Atlantic.— Dt. hydrogr. Z. 21:

109-117.

SHACKLETON, N. J. 1969. The last interglacial in the marine and terrestrial records. — Proc. r.

Soc. Lond. B. 174: 135-154.

SHACKLETON, N. J. & OppykgE, N. D. 1973. Oxygen isotope and palaeomagnetic stratigraphy

of equatorial Pacific core V 28-238: Oxygen isotope temperatures and ice volumes on a

10° year and 10° year scale.— Quatern. Res. 3: 39-55.

SHANNON, L. V. 1966. Hydrology of the south and west coasts of South Africa. —Jnvestl.

Rep. Div. Sea Fish., S. Afr. 58: 1-22.

STANLEY, S. M. 1970. Relation of shell form to life habits of the Bivalvia (Mollusca).— Mem

geol. Soc. Am. 125: 1-296.

SVERDRUP, H. U., JOHNSON, M. W. & FLEMING, R. H. 1942. The oceans, their physics, chemistry,

and general biology. New York: Prentice-Hall.

TANKARD, A. J. & SCHWEITZER, F. R. 1974. The geology of Die Kelders cave and environs:

a palaeoenvironmental study.—S. Afr. J. Sci. 70: 365-369.

VALENTINE, J. W. 1955. Upwellirig and thermally anomalous Pacific coast Pleistocene molluscan

faunas.—Am. J. Sci. 253: 462-474.

VALENTINE, J. W. 1957. Late Pleistocene faunas from the northwestern coast of Baja California,

Mexico.— Mem. S. Diego Soc. nat. Hist. 12: 289-308.

VALENTINE, J. W. 1961. Paleoecologic molluscan geography of the Californian Pleistocene. —

Univ. Calif. Publs geol. Sci. 34: 309-442.

VALENTINE, J. W. 1971. Resource supply and species diversity patterns.—Lethaia 4: 51-61.

VALENTINE, J. W. & MEADE, R. F. 1961. California Pleistocene paleotemperature.— Univ.

Calif. Publs Bull. Dep. Geol. 40: 1-46.

VAN ZINDEREN BAKKER, E. M. 1967. Upper Pleistocene and Holocene stratigraphy and ecology

on the basis of vegetation changes in sub-Saharan Africa. Jn: Bishop, W. W. and Clark,

J. D. eds. Background to evolution in Africa: 125-147. Chicago: University of Chicago

Press.

VAN ZINDEREN BAKKER, E. M. (in press). The origin and palaeoenvironment of the Namib

Desert biome. —J. Biogeogr.

WAGNER, P. E. & MERENSKY, H. 1928. The diamond deposits on the coast of Little Namaqua-

land.—Trans. geol. Soc. S. Afr. 31: 1-35.

Wicgour, K. M. & YonGE, C. M. eds. 1964. Physiology of Mollusca. Vol. 1. New York: Academic

Press.

ZINSMEISTER, W. J. 1974. A new interpretation of thermally anomalous molluscan assemblages

of the California Pleistocene.—J. Paleont. 48: 84-94.

6. SYSTEMATIC papers must conform with the International code of zoological nomenclature

(particularly Articles 22 and 51).

Names of new taxa, combinations, synonyms, etc., when used for the first time, must be

followed by the appropriate Latin (not English) abbreviation, e.g. gen. n., sp. n., comb. n.,

syn. n., etc.

An author’s name when cited must follow the name of the taxon without intervening

punctuation and not be abbreviated; if the year is added, a comma must separate author’s

name and year. The author’s name (and date, if cited) must be placed in parentheses if a

species or subspecies is transferred from its original genus. The name of a subsequent user of

a scientific name must be separated from the scientific name by a colon.

Synonymy arrangement should be according to chronology of names, i.e. all published

scientific names by which the species previously has been designated are listed in chronological

order, with all references to that name following in chronological order, e.g.:

Family Nuculanidae

Nuculana (Lembulus) bicuspidata (Gould, 1845)

Figs 14-15A

Nucula (Leda) bicuspidata Gould, 1845: 37.

Leda plicifera A. Adams, 1856: 50.

Laeda bicuspidata Hanley, 1859: 118, pl. 228 (fig. 73). Sowerby, 1871: pl. 2 (figs 8a—b).

Nucula largillierti Philippi, 1861: 87

Leda bicuspidata: Nicklés, 1950: 163, fig. 301; 1955: 110. Barnard, 1964: 234, figs 8-9.

Note punctuation in the above example:

comma separates author’s name and year

semicolon separates more than one reference by the same author

full stop separates references by different authors ;

figures of plates are enclosed in parentheses to distinguish them from text-figures

dash, not comma, separates consecutive numbers

Synonymy arrangement according to chronology of bibliographic references, whereby

the year is placed in front of each entry, and the synonym repeated in full for each entry, is

not acceptable.

In describing new species, one specimen must be designated as the holotype; other speci-

mens mentioned in the original description are to be designated paratypes; additional material

not regarded as paratypes should be listed separately. The complete data (registration number,

depository, description of specimen, locality, collector, date) of the holotype and paratypes

must be recorded, e.g.:

Holotype

SAM-A13535 in the South African Museum, Cape Town. Adult female from mid-tide region, King’s Beach,

Port Elizabeth (33.51S, 25.39E), collected by A. Smith, 15 January 1973.

Note standard form of writing South African Museum registration numbers and of date.

7. SPECIAL HOUSE RULES

Capital initial letters

(a) The Figures, Maps and Tables of the paper when referred to in the text

e.g. *... the Figure depicting C. namacolus .. .’

*...in C. namacolus (Fig. 10)...’

(b) The prefixes of prefixed surnames in all languages, when used in the text, if not preceded

by initials or full names

e.g. Du Toit but A. L. du Toit

Von Huene but F. von Huene

e.g. Therocephalia, but therocephalian

Punctuation should be loose, omitting all not strictly necessary

Reference to the author should be expressed in the third person

Roman numerals should be converted to arabic, except when forming part of the title of a

book or article, such as

‘Revision of the Crustacea. Part VIII. The Amphipoda.’

Specific name must not stand alone, but be preceded by the generic name or its abbreviation

to initial capital letter, provided the same generic name is used consecutively.